Error When Add Resource to a Group

[joaoantunes87]

Hi,

I have install RHQ Server version: 3.0.0.B03
                                              build number: b2804ea.

After create a group a try add some resources but appear an error i don't understand.

When i click "ADD TO GROUP" appear this:

With this stack trace:

I know this is not the best way to expose the problem, but i don't understand what can be the error. Someone know the solution?

Thanks,

Joao Antunes